In the sector of the mosaic art, some work patterns, which used to be completed during the laying stage, are currently prepared prior to this stage.
In practice, the tesserae (or the other similar elements that make up a pattern, an ornament, etc.) are orderly grouped into lists of established dimensions and kept united by strips of opaque paper glued on the exposed or upper face of the tesserae.
Upon their disposition into place, such lists must be fixed on the surfaces to be coated, the latter being suitably treated with a binding agent. This operation may prove difficult to make and give rise to imperfections in the work because of the lack of a support able to guide the tesserae at the bottom and also because the strips, which keep the list of tesserae united, make it impossible to catch sight of the underlying tesserae.
The above indicated drawbacks may, therefore, contribute to deform, during the laying stage, the pattern previously composed with the tesserae, and/or induce errors in the junctions between the various portions of a given pattern.